3

I have a relatively new Bottecchia bicycle, about a year and a half year old and underwent about 8,000km.

I almost always use the biggest cog on the front cassette. Lately I noticed that as I apply a lot of torque, i.e. when accelerating from a stop (in high gear), or surely when I stand up, the chain slips -- at least that's what I think that's happening. What I actually experience is a cracking noise, the pedals don't effect the chain for a split second, and then it's back to normal. It is important to say that it doesn't happen to me if I switch to a lower gear on the front crank (but it doesn't matter which gear I'm on at the rear).

I have several ideas as to what may cause the problem. Firstly I thought it may have to do with broken or worn off cog. That is possible because I think I may have over-lubricated the chain last time, and I experienced a sand storm. However I think it may not be the case because it happens regardless of where my pedals are (if I had one broken teeth, for example, I would expect it to happen only when my right pedal is at, say, 7 o'clock or something).

Another possible reason is that maybe I have a problem with the front derailleur -- as I started using the middle gear more often, I noticed that I have problems getting back to the top gear (no problem going down) -- I hear cranking sounds, and often it wouldn't shift until I push the shifter further (even though it doesn't move further, it probably pushes the derailleur a bit, enough to make the jump). It also happened once or twice that under torque the chain slipped to the middle gear.

Third reason I could think of is a worn off chain -- as I said it has served me for probably around 8,000km, and I also noticed there's a noticeable gap between the chain and the wheel (I'll post pictures shortly).

enter image description here

Here are some pictures I took. I hope they're helpful in identifying the cause of it, if not I can take more.

Thank you very much!

3

Your first image suggests the chain is not meshing properly with the chain ring. After 8000 km you should be either just finished your fourth chain, or about halfway through the second (depending on if your manufacture says 2000 or 5000 km per chain.) How long since the chain was changed?

Do a chain length check too - 24 half-links (12 pairs of inside and outside) should be 12 inches long. Any more than 12 1/8th inches is too stretched. Running a worn chain normally wears out the rear cassette, whereas the front ones tend to survive because of the greater number of teeth.

Finally - use a straight-edge and confirm the front chainring is not bent. This can be seen by eye if you turn the pedals while looking down from above. A deflection could cause a bad meshing.

Over-lubing itself is not as issue. However it attracts dust dirt and sand, which can do mischief on the chain, accelerating wear. Best practice is to clean the chain, dry the chain, and then oil the chain.

  • Thanks! I am a bit embarrassed to say I haven't changed the chain at all. I just use it to commute every day so I don't maintain it that well. So first I wonder if there are different chain sizes/lengths and if so, how can I tell mine? Secondly, could that be the cause for my problem? Or should I just replace it because, well, it's time? – user3694188 Sep 21 '15 at 7:45
  • @user3694188 If that is the case, then it is likely that you are going to have to replace the chain AND the chainring. When the chain is worn, it won't mesh properly with the chainring, the result is that the chain only sits on the top of the teeth. These then wear faster, resulting in both your chain and your chainring being ruined. – Aron Sep 21 '15 at 9:46
  • You might be lucky on the chainring but the (rear) cassette will need looking over as well. I trashed mine with 5000km on one chain, but the chainrings were fine (slightly heavy rider and using the full range of gears on every commute) – Chris H Sep 21 '15 at 10:16
  • 1
    24 links in 12", not 12 links. – BSO rider Sep 21 '15 at 21:37
  • @BSOrider Thank you - I've clarified that now. – Criggie Sep 21 '15 at 22:43

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.